package DataStructure.priority;

public class MaxPriorityQueue<T extends Comparable<T>> {
    private T[] items;
    private int N;

    public MaxPriorityQueue(int capacity){
        this.items=(T[])new Comparable[capacity+1];
        this.N=0;
    }

    public int size(){
        return N;
    }

    public boolean isEmpty(){
        return N==0;
    }

    private boolean less(int i,int j){
        return items[i].compareTo(items[j])<0;
    }

    private void exch(int i,int j){
        T temp=items[i];
        items[i]=items[j];
        items[j]=temp;
    }

    public void insert(T t){
        items[++N]=t;
        swim(N);
    }

    //删除最大元素并返回
    public T delMax(){
        T max=items[1];
        exch(1,N);
        N--;
        sink(1);
        return max;
    }

    //上浮k处的元素
    private void swim(int k){
        while (k>1){
            if(less(k/2,k)){
                exch(k/2,k);
            }
            k=k/2;
        }
    }

    private void sink(int k){
        while (2*k<=N){
            int max;
            if(2*k+1<=N){
                if(less(2*k,2*k+1)){
                    max=2*k+1;
                }else {
                    max=2*k;
                }
            }else{
                max=2*k;
            }

            if(!less(k,max)){
                break;
            }
            exch(k,max);
            k=max;
        }
    }
}
